The present invention relates to a self-inflatable air cushion for use in shoes, and more particularly to such an air cushion which includes a pump in the form of a collapsible plenum chamber, a support chamber surrounding the pump, and a valve connected between the pump and the support chamber for permitting air to be driven from the pump into the support chamber by compressing the pump with the foot of the user.
A conventional air cushion of this type is generally comprised of a collapsible three-dimensional body defining a plurality of air cells and a plurality of passages connecting the air cells. An air valve is also connected to the passages and disposed outside the sole of the shoe. When the air cushion is to be inflated, an air pump is attached to the air valve and operated to pump air into the air cells. If the inside pressure of the air cushion is excessively high, it cannot be regulated. Moreover, known cushions of this type may also include a pump which is surrounded by a support chamber that is also inflated by the pump. However, this known construction has a distinct disadvantage in that the chamber surrounding the pump is a of a two-dimensional configuration until it has been inflated by the pump. Accordingly, the chamber is always softer than the pump until inflation has been realized. Conventional cushions of this type are incapable of providing stable support for the foot of the user until the cushion has been sufficiently inflated with air.
It is an object of the present invention to provide a self-inflatable air cushion which comprises a pump in the form of a collapsible plenum chamber having an air hole, a support chamber surrounding the pump, an air passage providing communication between the support chamber and the pump, and an one-way valve disposed in the air passage for permitting air to pass from the pump to the support chamber. When the pump is compressed by the foot of the user, air is forced out of the pump through the one-way valve and into the support chamber. When the foot is released, outside air is drawn into the pump through the air hole. In this way, the firmness of the support chamber may be adjusted. The support chamber is formed from an appropriate material, such as a polymer plastic, which permits it to maintain a preformed three-dimensional structure having sufficient rigidity to provide support for the foot of the user before it has received compressed air from the pump.
According to another object of the invention, a relief valve or pressure regulating chamber is provided to regulate the inside pressure of the support chamber to a desired level.
A still further object of the present invention includes providing a pressure accumulation chamber which has one end connected to the pump through an one-way valve for permitting air to flow from the pump to the pressure accumulation chamber, and an opposite end connected to the support chamber through an one-way valve for permitting air to flow from the pressure accumulation chamber to the support chamber. When the pump is compressed, compressed air is driven from the pump chamber into the pressure accumulation chamber. Since the support chamber is simultaneously subjected to an external pressure, the compressed air pressure of the pressure accumulation chamber is prevented from passing to the support chamber. When the external pressure is released from the support chamber, the compressed air of the pressure accumulation chamber is permitted to pass to the interior of the support chamber.